1. Field of Invention
This invention relates to spouts for portable gasoline containers which are used to re-fuel off-road power equipment such as tractors, lawn mowers, chainsaws, outboard motors, etc.
2. Background of the Invention
Gasoline spillage while refueling off-road power equipment is a frequent occurrence, and a source of irritation and worry to the operator, since gasoline is highly flammable and explosive. The presence of hot engine components adds to this concern. The problem arises from a combination of poor visibility of the rising fuel level in the vehicle fuel tank, combined with the operator's natural desire to finish the refueling as quickly as possible, while still filling the tank completely.
An increasing problem is the effect on air quality. The spilled fuel quickly evaporates, producing a volume of vapor several times larger than that of the spilled liquid fuel. The effect in a single case of spillage is small, but when multiplied by the large number of off-road gasoline-powered engines, some of which are refueled several times a day, the effects on air quality are significant.
Some states, notably California and Massachusetts, now require that portable gasoline containers sold in their states be un-vented, and equipped with an automatic shutoff spout which is spill-proof and able to capture fuel vapor as it is displaced from the fuel tanks of off-road, internal combustion engines by the incoming liquid fuel. It is predicted by some knowledgeable people in the industry that most states will follow with similar requirements within a few years.
Inventors have responded with various schemes to solve this problem. U.S. Pat. No. 6,318,604, to Messner et al depends upon a manual shut-off valve which fails to meet California's requirement of automatic shutoff. Spills can occur if the user does not release the valve when the tank is full and, as pointed out earlier, it is often difficult, under adverse lighting conditions, to observe the rapidly rising fuel level in the small openings found in most fuel tanks.
All of the prior art devices discovered rely upon developing a partial vacuum within the portable fuel container at some time during the re-fueling procedure. The resulting pressure differential, between atmospheric pressure and container pressure, is intended to support the head (weight) of the gasoline remaining in the container after the vent tube opening is blocked by rising fuel in the tank.
There are three serious limitations of partial container-vacuum systems, either or all, of which are characteristic of the prior art devices:    1. Devices which initiate the development of the partial vacuum after the fuel level reaches the vent tube entrance level can, and do, allow serious overfill spillage when the volume of air left in the container is large. Boyle's gas law states that in a closed system, at constant temperature, the absolute pressure of a gas, multiplied by its volume, is a constant. Application of this principle reveals that, when a gallon or more of fuel has been poured from the container, the volume of vapor and air mixture remaining in the container must be expanded as much as 5 to 8 cubic inches before a partial vacuum capable of stopping the flow of fuel is developed. This is especially true when an initial volume of vapor and air in the container, in addition to that of the poured fuel, is accounted for. This expansion requires an equal volume of fuel flow, and is a major reason why many of the prior-art devices fail to control spillage.    2. Attempts to avoid this problem by restricting the rate of vapor and air flow to the container while refueling, and thus to develop and maintain the partial vacuum during the entire time when the fuel is flowing, suffer from a different but equally annoying problem. Restriction of vapor and air flow to the container during refueling necessarily reduces the rate of fuel flow from the container. This slows refueling and is very tiring to a user holding the heavy container in an awkward position. Tests have revealed a flow rate as low as one gallon a minute with this type of device which is a burden when refueling a large garden tractor.    3. Open-system devices, which fail to seal the tank from the atmosphere, allow the vapor to follow the path of least resistance and, since it is lighter than air, it is free to move upward and out of the tank while the heavier air can move downward into the vicinity of the vent tube. This is even more likely to happen on a windy day, with the result that much of the air entering the vent tube may be atmospheric air rather than gasoline-vapor laden air. It is axiomatic that any vapor volume which is not allowed to return to the container must escape to the atmosphere with an open-system, sacrificing much of the initial purpose of the device. All of the prior art devices are open-system devices and thus fail under this criterion.
U.S. Pat. No. 5,228,487 to Thiermann et al was one device with which a flow rate of only one gallon per minute was recorded during tests. U.S. Pat. Nos. 4,834,151, 5,076,333, 5,249,611, and 5,419,378 to Law rely upon a capillary to restrict vapor flow to the container, yet these fail to prevent spills even with the restricted vapor flow and resulting decreased fuel flow rate. U.S. Pat. No. 6,318,604 to Messner et al is also an open-system device. It is axiomatic that any vapor volume which is not allowed to return to the container must escape to the atmosphere with an open system, sacrificing part of the initial purpose.
The California specifications require an un-vented container in order to reduce fuel vapor contamination of the atmosphere during storage of the container. On a hot day an un-vented container of gasoline can develop a high vapor pressure, especially if left sitting in the sun. To avoid a sudden surge of fuel into the tank and the danger of spillage when initiating the refueling process, the user of prior-art devices is cautioned to open the shutoff valve by hand while the container is still in the upright position, with the spout pointing away from the user, to release the pressurized vapor into the atmosphere. Obviously, this sacrifices again some of the initial purpose of the spout design.
While the vapor pressure is temporarily relieved by this action the container fuel is only partly cooled down. Container pressure will immediately build up again to the vapor pressure of the still-warm fuel. The possibility of creating a partial vacuum within the container of warm gasoline is certainly in question, and the probability of fuel spillage is again apparent.
The problems outlined above will occur with any device which relies on a partial container vacuum to stop fuel flow, and which allows the fuel tank opening to remain exposed to the atmosphere while refueling. Each of the prior art devices, which claim to provide spill-proof refueling of off-road power equipment, suffers from one or more of the deficiencies described above.